In the manufacture of an articulated, predominantly concrete mat, which comprises concrete blocks and a flexible geogrid embedded in such blocks and in which the flexible geogrid defines flexible members connecting such blocks to one another, an intermediate article being a concrete slab is cast, in which a flexible geogrid is embedded. The slab has relatively thinner portions, along which the slab is breakable to form such blocks, and relatively thicker portions, which become such blocks when the slab is broken along the relatively thinner portions. The relatively thicker portions are arranged in parallel rows and are staggered in adjacent rows, before the slab is broken therealong, and the relatively thicker portions in alternate rows are aligned in parallel columns, before the slab is broken therealong.